i'm getting a 455 out of a 75 catalina. it should have 5C heads. i'm thinking about putting a comp cam with about 230-240 duration at .050 in and having about 10:1 compression. how well do you think it will perform with the 5c heads cleaned up a little, a decent exhaust and intake, and i'l probably have it balanced?

 

i am not a Pontiac encyclopedia, but just about anything from the mids 70's = SMOG. i would plan on more than a little cleaning up...but upping that compression will be a big plus. you just may run into issues with a cam that outflows the heads it is breathing through

 

the 5c heads are suposed to be pretty good. they flow something like 230cfm. it'l spin the tires in any gear on the catalina. somebody made about 500hp with cleaned up 5c heads and a roller cam.

 

heres some flow numbers from a 5C head at 12inches
5C_Unported_Heads
0
6
1 2.110000
1 12.000000
1 0.100000
1 0.200000
1 0.300000
1 0.400000
1 0.500000
1 0.600000
1 63.000000
1 115.000000
1 143.000000
1 161.000000
1 164.000000
1 170.000000<.600 lift
1 1.770000
1 12.000000
1 0.100000
1 0.200000
1 0.300000
1 0.400000
1 0.500000
1 0.600000
1 42.000000
1 78.000000
1 103.000000
1 118.000000
1 127.000000
1 131.000000

 

I read somewhere that 6x heads were the best heads at the time for a smog head.But finding them might be a problem since indian motors are not a dime a dozen anymore.

 

i'l have 2 sets of 6x heads, one is going on a '80 i'm going to sell and the other i'l have to do whatever i want with it. i thought the 5C's where better though.

 

oh yea, and i got the 455 and a th400 tranny for $400(traded for an old truck i had). the engine runs good too. i also got a '80 and '78 for 1k(traded for a 78 malibu i had) the '80 i'm using for parts, its got a 301 and th350 but the 78 has a 400 and th350. the 78 hit a tree so i'm putting all of the front end stuff from the 80 on the 78 and putting the 400 from the 78 in another 80 i found for 750 in good condition without the engine and tranny but included the 6x heads and some other parts. found all of this stuff in about 2 weeks.

 

heres some more flow numbers i found. i think it was all done at 12 inches.


5C
Intake(D) Flow(cfm) Exhaust(S) Flow (cfm) Exh./Int.
.100 63 63 .100 42 .67
.200 115 115 .200 78 .68
.300 143 146 .300 103 .71
.400 161 160 .400 118 .74
.500 164 165 .500 127 .77
.600 170 169 .600 131 .77

6X
Intake(S) Flow (cfm) Exhaust(S) Flow (cfm) Exh./Int.
.100 67 .100 51 .76
.200 112 .200 83 .74
.300 140 .300 96 .67
.400 158 .400 104 .66
.500 163 .500 110 .67
.600 167 .600 113 .68